Coal has been mined in Wales since Roman times. In terms of importance it was secondary to iron but later it came to dominate the economy. Production spread to the Rhondda valleys where the rich coal seams lay so deep that they had been thought to be unworkable. The first coal from the Rhondda was sent to Cardiff in AD 1855 and after that pits opened up all over the valleys employing as many as 24,000 miners (though at their peak and in post-war years there was a far greater number). Explosions and roof falls meant that mining was a dangerous occupation.

The expanding railways and the change from sail to steam on the high seas were responsible for much of the demand but steam power was also used in many other industries. Pitheads with their winding towers marked every pit village and by the early 20th century there were coal tips everywhere.

The mighty coal industry began to decline in 1945 partly because the pits were too small to accommodate modern excavating machinery. Output fell but efforts were made to revive the industry and mining continued for a few more decades. The replacement of coal with oil and gas for heating sounded the death knell of the coal industry as late as the 1980s.